The present invention relates generally to an improved data processing apparatus and method and more specifically to mechanisms for managing and balancing load across multiple managed systems in a logical partitioning data processing system.
A logical partition, commonly called an LPAR, is a subset of computer's hardware resources, virtualized as a separate computer. In effect, a physical machine can be partitioned into multiple logical partitions, each hosting a separate operating system. Logical partitioning divides hardware resources. Two LPARs may access memory from a common memory chip, provided that the ranges of addresses directly accessible to each do not overlap. One partition may indirectly control memory controlled by a second partition, but only by commanding a process in that partition. CPUs may be dedicated to a single LPAR or shared.
The changing of resource allocations without restart of the logical partition is called dynamic logical partitioning (DLPAR). DLPAR is the capability of reconfiguring a logical partition dynamically without having to shut down the operating system that runs in the LPAR. DLPAR enables memory, CPU capacity, and I/O interfaces to be moved non-disruptively between LPARs within the same server.
Live partition mobility (LPM) is a feature of IBM POWER6® and POWER7® servers that allows an active LPAR to be relocated from one system to another without being deactivated, “POWER6” and “POWER7” are trademarks of International Business Machines Corporation in the United States and other countries. The source and target systems must have access to the same network and storage area networks but need not be of the same type. Any sized partition can be moved; essentially, memory content of the partition is copied asynchronously from one system to another to create a clone of the partition, with “dirty” pages being re-copied as necessary. When a threshold is reached (i.e., when a high percentage of the pages have been successfully copied across), the partition is transitioned to the target machine and any remaining pages are copied across synchronously.